Standard for use in testing for captan.
Environmental testing requirements call for the determination of low levels of the fungicide captan and the related captafol. These compounds are readily hydrolyzed and thus unstable in aqueous media. This instability makes it very difficult to devise standards for detecting small amounts of these materials by immunoassay. Captan has the structure THPD--S--CCl.sub.3 and captafol has the structure THPD--S--CCl.sub.2 --CH.Cl.sub.2, wherein THPD is the cis-1,2,3,6-tetrahydrophthalimido moiety. In order to carry out immunoassay tests for captan, which type of assay is most useful in detecting very small amounts of an unknown material, it would be necessary to provide a water stable analog of captan which is reactive with the antibody used in the method. It has been found by the work disclosed and claimed herein, that such a standard can be provided by a material having the structure EQU THPD--(CH.sub.2).sub.x --(R.sup.3).sub.y --R.sup.1 (I)
wherein THPD is cis-1,2,3,6-tetrahydrophthalimido, x is an integer from 1 to 10, R.sup.1 selected from the group consisting of --COOH, --NH.sub.2, --NO.sub.2, --SH and --OH, R.sup.3 is an aryl moiety and y is 0 or 1. Several compounds within this general structure wherein R.sup.1 is carboxyl are reported in the literature, in particular those wherein x has the value 2, 1, 3, and 5. The method of synthesis involves the condensation of tetrahydrophthalic anhydride with an equimolar amount of the corresponding amino alkanoic acid. The literature however appears to be silent on any immunological relationship between compounds of formula (I) and captan or captafol.